Machining :

Machining is an occupation or hobby or a class of material-working processes that involves using a power-driven machine tool, such as a lathe, milling machine or drill, to shape metal. Machining is a part of the manufacture of almost all metal products. Some plastic parts are machined. A person who specializes in machining is called a machinist.

A room, building, or company where machining is done is called a machine shop.

Machining operations :

Most machining operations can be divided into those that remove metal from an item, and those that form metal in an item.

Often an unfinished workpiece will need to have some parts removed or scraped away in order to create a finished product. For example, a lathe is a machine tool that generates circular sections by rotating a metal workpiece, so that a cutting tool can peel metal off, creating a smooth, round surface. A drill or punch press can be used to remove metal in the shape of a hole. Other tools that may be used for various types of metal removal are milling machines, saws, and grinding tools. Many of these same techniques are used in woodworking.

Metal can be formed into a desired shape much more easily than materials such as wood or stone, especially when the metal is heated. A machinist may use a forging machine to hammer or mold a hot metal workpiece into a desired shape. Dies or molds may be used if the metal is soft enough, or under high pressures. A press is used to flatten a piece of metal into a desired shape.

Advanced machining operations might use electrical discharge, elecro-chemical erosion, or laser cutting to shape metal workpieces.

As a commercial venture, machining is generally performed in a machine shop, which consists of one or more workrooms containing major machine tools. Although a machine shop can be a stand alone operation, many businesses maintain internal machine shops which support specialized needs of the business.

The inferior finish found on the machined surface of a workpiece may be caused by insufficient clamping, cutting conditions or perhaps an incorrectly adjusted machine. It is evident by an undulating or irregular finish, and the appearance of waves on the surface.